The militias, which the elected parliament branded as "terrorists", said the house had lost its legitimacy through its alleged complicity with a deadly air strike on the airport that the Islamists blamed on Egypt and the United Arab Emirates.

"The Emirates and Egypt are implicated in this cowardly aggression," Mohammed Hadia, spokesperson for the Fajr Libya (Libya Dawn) militia, said late on Saturday.

Parliament, for its part, fired back at the militias which announced their seizure of Tripoli airport after a weeks-long battle against nationalist rivals for control of the strategic facility.

"The groups acting under the names of Fajr Libya and Ansar al-Sharia are terrorist groups and outlaws that are rising up against the legitimate powers," parliament charged in a statement.

The parliament, which sits in Tobruk, 1 600km east of the capital, said it was determined to deal with the challenge through the regular armed forces.

Fajr Libya is a coalition of Islamist militias, mainly from Misrata, east of the capital, while Ansar al-Sharia, which Washington also brands a terrorist group, controls around 80% of the eastern city of Benghazi.

"These two groups are a legitimate target of the national army, which we strongly support in its war to force them to halt their killings and hand over their arms," MPs said.

Fajr Libya said on Saturday it had captured Tripoli's battered international airport.

The announcement came a day after an unidentified warplane raided Islamist positions around the airport, killing 13 fighters, according to Fajr Libya which says it is defending the gains of the 2011 revolution.

The fall of the airport would be a major defeat for the nationalist fighters from Zintan, southwest of Tripoli, who have held it since the overthrow of long-time dictator Muammar Gaddafi in 2011.

Early on Sunday, Islamist militiamen attacked the Tripoli studios of private television station Al-Assima which supports the Zintan nationalists and kidnapped staff, the station said.

Al-Assima, in a news bulletin, said equipment was destroyed and staff were missing.

On the political front, the outgoing provisional General National Congress (GNC), which was dominated by Islamists, was to resume operations at the request of Fajr Libya, despite being superseded by parliament, its spokesperson said.

Its members were summoned to meet in Tripoli, adding to the political chaos in Libya and splitting the North African state into two centres of power.

Sisi denies Egyptian involvement

Tripoli airport, 30km south of the Libyan capital, has been shut since 13 July because of the deadly clashes between the Islamists and the Zintan force.

The Islamist fighters charged that the provisional government and parliament had both lost legitimacy through an act of "treason" with their alleged approval of foreign intervention.

Egypt on Sunday denied any role in the air raid.

President Abdel Fattah al-Sisi, quoted by state news agency MENA, said: "There are no Egyptian aircraft or forces in Libya and no Egyptian aircraft participated in military action inside Libya."

There was no early reaction from the Emirates, an ally of Egypt against Islamist extremism.

The foreign ministry in Cairo said on Sunday it would host a meeting Monday of the foreign ministers of Libya, Egypt, and Algeria, Tunisia, Sudan, Chad and Niger, all of which border Libya.

The battle for Tripoli airport was the fiercest in the capital since the revolt three years ago that ousted the Gaddafi regime.

On 27 April, the health ministry said the first two weeks of clashes had killed almost 100 people and wounded 400.

The Islamists aim to capitalise on their military success with a return to the political front after their defeat at the ballot box in 25 June polls.